The invention relates to a suction duct for textile machines, in particular for a bale-opener. The suction duct possesses a stationary connection-opening and a movable connection-opening which is located in a longitudinal side of the suction duct and is portion of a longitudinal slot. The longitudinal slot can be closed by means of a flexible cover-strip, one end of this strip being fastened at a fixed point.
For drawing off fiber material by suction, the use of a suction duct with stationary and movable connection-openings is known. The stationary opening being for the connection to a pneumatic conveying apparatus and the movable opening being on its upper side. The movable connection-opening, through which the fiber material is led into the suction duct, is a portion of a continuous longitudinal slot (German Offenlegungsschrift No. 2,944,889). The longitudinal slot and, hence, the interior space of this suction duct which, in particular, is intended for a bale-opener, is sealed off with respect to the outside air by means of a flexible cover-strip. The two ends of the cover strip are fastened to the ends of the suction duct. The cover-strip is guided by means of reversing rollers, in a manner such that over a section of the longitudinal slot, it leaves the movable connection-opening free, in the form of an intervening space, and lies, on both sides of this intervening space, in two layers, one upon the other, the upper layer being configured in a manner permitting it to move. This arrangement is intended to enable the intervening space to be shifted with a low expenditure of power.
However, due to the relative movement between the upper strand of the cover-strip and the lower strand, the latter closing the longitudinal slot, this arrangement leads to increased wear on the strip. A further disadvantage is the high material-related expenditure resulting, in particular, from the great length of the cover-strip, the numerous reversing and supporting rollers for the strip, and the extensive sealing arrangements which are necessary in the region of the points at which the strip is reversed, as well as the increased space requirement which is necessary for tensioning the long cover-strip. Moreover, this design of strip-guidance system permits a transport or removal tube at one end of the suction duct. This tube leads to a suction device and is connected laterally and impedes access to the suction duct for maintenance work.
These disadvantages are also exhibited by another known suction duct which is designed in the same manner as the duct just mentioned and which is employed for supplying suction-air to a cleaning or maintenance appliance which can be moved along a textile machine; for example, a knotter, at the individual working positions on the machine (British Pat. No. 1,385,618).